The invention relates to not only new wells, but also to revitalizing preexisting vertical and horizontal oil and gas vertical wells that have been depleted or are no longer profitable, by improving the porosities of the wells"" payzone formations. This is accomplished by providing a micro channel through the already existing casing, and out into the formation.
After a well has been drilled, completed, and brought on-line for production, it may produce oil and gas for an unknown period of time. It will continue to produce hydrocarbons, until the production drops below a limit that proves to be no longer profitable to continue producing, or it may stop producing altogether. When this happens, the well is either abandoned or stimulated in a proven and acceptable process. Two of these processes are called Acidizing and Fracturizing. Acidizing uses an acid to eat away a channel in the formation thus allowing the hydrocarbons an easier access back to the well bore. Fracturizing uses hydraulic pressure to actually crack and split the formation along preexisting cracks in the formation. Both of these methods increase the formation""s porosity by producing channels into the formation allowing the hydrocarbons to flow easier towards the annulus of the well which increases the production of the well along with it""s value. However, the success of these operations is highly speculative. In some wells, it may increase the production rate of a well many times over that of its previous record, but in others, they may kill the well forever. In the latter case the well must be plugged and abandoned. Both Acidizing and Fracturizing are very expensive. Both require dedicated heavy mobile equipment, such as pump trucks, water trucks, holding tanks, cranes along with a large crew of specialized personnel to operate the equipment.
A more efficient method of stimulating a vertical well is to drill a hole in the well casing, and then bore a micro-horizontal channel into the payzone using a high pressure water jet to produce a channel for the hydrocarbons to follow back to the well bore""s annulus. Once an initial lateral hole through the already existing casing, has been produced. The micro drill must be brought back to the surface. Then a high pressure water jet nozzle is lowered into the well and through the above-mentioned hole in the casing and out into the payzone. It then produces a finite lengthened channel out radially away from the well bore into the payzone. Once this is completed, it to must be brought back to the surface.
Because of the limitations of the present technology, the entire drill string is then manually rotated from the surface to blindly rotate the drill shoe (located at the bottom of the drill string) for the next drilling and boring operation. The process is repeated until the desired number of holes/bores has been reached.
It is very difficult and imperfect to rotate an entire drill string, so that the exit hole of the shoe, which is located at the bottom of the drill string, is pointing exactly in the desired direction. For example, if the well casing is tilted or off-line, the drill string may bind so that the top portion rotates while the bottom portion (including the shoe) may not actually move or move less than the rotation at the surface. This is due to the fact that all of the applied torque does not reach completely to the bottom of the drill string due to friction encountered up hole from the shoe.
The invention provides a method and apparatus that allows the for the drilling and completion of a plurality of lateral holes in the well casing in one step, removal of the drill, then lowering of the blasting nozzle and re-entering each of the holes in succession to horizontally bore into the formation without interruptions or without having to turn the entire drill string at the surface to realign with each hole.
In accordance with the invention, the shoe assembly consists of a fixed section and a rotating working section. The fixed section is threaded into the down hole end of upset tubing, such as straight tubing or coiled tubing or any other method known in the art, to lower the entire shoe assembly to a desired depth. The fixed section provides a central channel or passage to allow a drill apparatus (with a flexible drill shaft and a special cutting tool) to be inserted into the assembly.
The rotatable working section is attached to the fixed section by a specially designed guide housing and ring gear that facilitates the turning of the turns the rotating section within the well casing. The ring gear converts the rotation of a motor driven transfer bar or drive shaft, turned by a self contained bi-directional variable speed DC motor, into rotation of this section. The DC motor is controlled by an operator at the surface and is powered by a self-contained lithium battery. The rotating section has a rotating vertical bore that passes through the center of the ring gear and into an elbow-shaped channel that changes the direction of the of the flexible shaft and cutter from a vertical entry into a horizontal exit to allow the drilling of holes in the well casing.
A gyroscope in the rotatable section communicates the precise angular position of the rotatable section to the operator on the surface via a multiconductor cable or by wireless transmission to allow the operator to align the rotating section to the desired position to cut the hole. The operator can then reorient the rotatable section of the shoe assembly for sequential drilling operations, if desired. When the drill is retracted and the water jet nozzle is then lowered back through the shoe, the operator again reorients the shoe assembly.
The drill apparatus, comprised of a housing, a shaft and a bit, may be of any type desired that will fit inside the upset tubing and through the shoe. The bit preferably is a hole cutter comprised of a hollow cylindrical body with a solid base at one end and a series of cutters or teeth at the other end. The terminal end of the body is serrated or otherwise provided with a cutting edge or edges. As the serrated edge of the cutter contacts the inside of the well casing, it begins to form a circular groove into the casing. As pressure is applied, the groove deepens until a disc (coupon) is cut out of the casing.
Sensors can be installed in the shoe assembly so that lights or alarming devices, on the operator""s console located at the surface can indicate a variety of information:
a. The drill has entered the shoe and is seated correctly.
b. The bit has cut through the casing and the hole is completed.
A core can be substituted for the hole cutter that would allow for the side of the casing and part of the formation to be cored. The cores could be brought to the surface to show the condition of the casing and the thickness of the cement. A mill can be substituted for the cutter to allow the casing to be cut in two if the casing was damaged. The use of a cutter and motor can be replaced with a series or battery of small shaped charges to produce the holes in the side of the casing. If the well bore is filled with liquid, the shoe can be modified to accept a commercial sonar device. This creates a system that can be rotated a full 360 degrees to reflect interior defects or imperfections. If the well bore is devoid of liquids, the shoe can be modified to accept a sealed video camera. This creates a system to provide a 360 degree view of all interior defects and imperfections.